Automatic control of a nonsynchronous cine fluororadiographic apparatus



8,1970: I I I IJjlc'nma, j 3,546,461; V V I AUTOMATIC CONTROlIjOF'A NONSYQNCHRONOUSCINE p I muonoamxoannmc APPARATUS -1-11ed 8ept. 13. 1968' I.

' MoIvIToRIM w a q APPARATUS STILL CAMERA I APPARATUS INTENSIFIER- V PHoTo IMER I0 z FLUORO VBRIGHTNESS CONTROL -Z8b l7 I 3T f VARIABL? 3lo COLLIMATOR. 30 V H MIil-fnlxgM SERVO TIMER SYSTEM: DENSITY I 32 x3") I coMPuTER E vARIz aLE MINI UM I LIMIT I TIMER BIAS swITcH V cIRcuIT I 32 u I Re r CONSTANT. I V POTENTIAL GENERATOR I r 7 300 I AuTo ATIc xv 7 JL EQ AIQ AUTOMATIC kv I I INVENTOR.

SERVO MOTOR I 2 JAMES R. CRAIG ATTORNEY United States Patent ,0

3,546,461 AUTOMATIC CONTROL OF A N ONSYN CHRONOUS CINE FLUORORADIOGRAPHIC APPARATUS James R. Craig, Glenview, Ill., assignor to Litton Medical Products, Inc., Des Plaines, Ill., a corporation of Delaware Filed Sept. 13, 1968, Ser. No. 759,643 Int. Cl. H05g 1/28 US. Cl. 250-95 14 Claims ABSTRACT OF THE DISCLOSURE A cine fluororadiographic apparatus for providing automatic regulation of the kv. applied across the secondary of the X-ray high voltage transformer. The apparatus is of a nonsynchronous type and is capable of operating at relatively high frame rates. A density computer is utilized to compare outputs from a phototimer, a maximum limit timer, and a minimum limit timer to provide a signal for automatic positioning of the kv. regulator to a desired setting.

FIELD OF THE INVENTION This invention relates to a cine fluororadiographic apparatus and more particularly to the automatic control of a nonsynchronous cine fluororadiographic apparatus.

DESCRIPTION OF THE PRIOR ART Pulsing systems to control the precise amount of X-ray radiation per film frame in X-ray cine systems are Well known. Two basic systems that have been employed are primary pulsing and secondary pulsing. Primary pulsing systems and secondary pulsing systems control the resp ctive power at the primary and the secondary of the X-ray high voltage transformer, respectively. As is well known, since the primary voltage is an alternating current, the primary pulsing systems are synchronous, i.e., the cameras are operated at 60, 30, 15 and 7 /2 frames per second. These systems have proven to be quite adequate for cine work on most studies operating in controlled exposure times of 16 milliseconds and beyond; however, when working with extremely fast moving parts of the body, for example, during a study of the heart valves or the cardiovascular system, Where the vessels and arteries move very rapidly as the heart pumps blood into them, the utilization of primary pulsing systems, coupled with their inherent relatively slow frame rates, have proven to be inadequate when operating in precisely controlled exposure times in the area of 3 to 5 milliseconds.

In the past, secondary pulsing systems have utilized either a pair of grid-controlled switch tubes, commonly referred to as secondary tetrodes, or a biased-controlled X- ray tube, commonly referred to as a grid-controlled tube, to control the power across the secondary of the X-ray high voltage transformer. Secondary pulsing systems employing the tetrodes have been utilized in cine X-ray systems having a variable pulse time from 2 to approximately 12 milliseconds, being nonsynchronous, indifferent of line frequency, and having a variable speed camera. Secondary pulsing systems employing the biased-controlled Xray tube have been utilized in cine X-ray systems having a variable pulse time from 2 to approximately 12 milli- 3,546,461 Patented Dec. 8, 1970 seconds, being nonsynchronous, and having a variable speed camera. In addition, other secondary pulsing systems also employing the biased-controlled X-ray tube have been utilized in cine X-ray systems having a fixed pulse time usually set at 4 milliseconds, being synchronous, and having cameras with speeds of 60, 30, 15 and 7 /2 frames per second.

Present cine X-ray systems for automatically controlling the density of X-ray films are of two basic types, one type automatically adjusts milliamperes (hereinafter referred to as Ina.) per frame, while the other type automatically adjusts the kilovoltage (hereinafter referred to as kv.) per frame. As is well known in the art, cine X-ray systems require a much greater degree of automatic density control since the density of the body part may be continuously changing, thus necessitating rapid changes in film speed rates and/or intensity that even a skilled technician could not adjust the factors fast enough.

Automatic ma. control has great limitations in that the practical range of varying ma. is not over 2 or 3:1. The minimum and maximum ma. levels are determined by the noise level or scintillation level of the image tube system and the X-ray tube thermal capacity, respectively. Most cine X-ray systems using automatic ma. control provide a center 0 type light meter which must be controlled by a skilled technician who manually adjusts the kilovoltage to maintain the 0 setting. On the other hand, the present automatic kv. control systems require a light sensing device which either reads peak light or integrates light and controls kv. in the primary of the high voltage transformer. These automatic kv. control systems utilize either a thyratron (or SCR) phase control or a motordriven variable automatic transformer. The automatic kv. control systems are more automatic than the automatic ma. control systems, but the automatic kv. control systems tend to hunt.

Since the present automatic kv. control systems control the primary of the high voltage transformer, they are not compatible with the nonsynchronous cine system and particularly not with systems having variable pulsed times as there has been no attempt to integrate time and intensity when the time and the frame rate vary as a means to control the kv.

As the use of cine X-ray has increased and medical techniques have been developed to a higher degree of pre cision for all parts of the body, it has become quite evident that nonsynchronous cine X-ray systems are desirable because of the demand to go beyond 60 frames per second. Furthermore, variable pulse times are desirable since techniques now require extremely short times at higher ma., While other techniques require longer times at lower ma. because of thermal limitations of the X-ray tube.

Accordingly, it is an object of the present invention to provide a novel cine fluororadiographic apparatus which is automatic and does not require a skilled technician.

It is another object of the present invention to provide a novel automatic cine fluororadiographic apparatus of the nonsychronous type operating at relatively high frame rates.

It is a still further object of the present invention to provide a novel automatic cine fluororadiographic apparatus having variable pulsed times.

It is another object of the preesnt invention to provide a novel nonsynchronous automatic cine fiuororadio graphic apparatus which integrates time and intensity for each cine frame and utilizes this information to automatically adjust the kv.

It is yet another object of the present invention to provide a novel automatic cine fiuororadiographic apparatus which acts instantaneously to changes in body part density as well as maintaining film control density over a wide range of body part thickness and body part density.

SUMMARY OF THE INVENTION In accordance with the objects set forth above, the present invention provides a cine fluororadiographic apparatus comprising a phototimer which integrates time and intensity for each cine frame, a density computer which receives the output of the phototimer along with the respective outputs of a maximum and a minimum timer, the density computer compares the three aforementioned outputs and provides a signal, when necessary, to automatically position the kv. regulator to a desired setting.

BRIEF DESCRIPTION OF THE DRAWING Additional objects, advantages, and characteristic features of the present invention will become readily apparent from the following detailed description of preferred embodiments of the invention when taken in conjunction with the accompanying drawing which is primarily a block diagram of a cine fluororadiographic apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawing, there is shown a cine fluororadiographic apparatus in accordance with the principles of the present invention. An X-ray tube 11 is shown along with the accompanying actuation circuits, shown in block diagram form, including a constant potential generator 12 and a bias switch circuit 13. The X-ray tube 11 is the well-known grid-controlled type. Lines 12a, 12b and 13a connect these circuits. A servo controlled collimator 14 along with a collimator servo system 15 is utilized to control the size of the X-ray beam 16 that is emitted from the X-ray tube 11. The aforementioned components are typical of X-ray generating apparatus well known in the art.

The numeral 17 designates the schematic representation of the patient who is undergoing X-ray diagnosis. As the X-ray beam 16 passes through the patient 17 and is picked up by a standard intensifier unit 18, the image which appears on an input phosphor 18a of the intensifier unit 18 is collimated by means of a combination of electron acceleration and minification so that the image is intensified to a factor of approximately 5,000 and appears on an output phosphor 18b. The image is then transferred to a standard lens arrangement which is well known in the cine X-ray art. The image may then be transferred via the lens arrangement to various recording or viewing devices, for example, a still camera apparatus 20, a moni toring apparatus 21 and cine camera apparatus 22. The still type camera apparatus 20 may be of a standard type known in the art which is utilized for recording a particular sequence of radiographs for observation at a later time. The monitoring apparatus 21 may include a vidicon for transferring the image to a television monitor or may be viewed directly on a fluoroscopic monitoring screen, neither of the aforementioned apparatus being shown in detail. The cine camera apparatus 22, of which this invention is primarily concerned, may be a 16 or 35 mm. variable frame rate camera, which along with a control circuit 23 is adapted to provide a movie record of the images appearing on the input phosphor 18a of the intensifier unit 18.

A fluoro kv. sensor 24, or standard photodiode, is adapted within the lens arrangement 19 to sense the intensity of the image within the lens arrangement 19. The

signal picked up by the fluoro sensor 24 may be applied to a fluoro brightness control 25 via line 25a. The output of the fluoro brightness control 25 may then be applied to an automatic kv. servomotor 26 via line 25b. The automatic kv. servomotor 26 is shown as part of a block diagram along with an automatic kv. regulator 27 which is utilized to control the constant potential generator 12, via line 27a, and thus, the kv. potential eventually applied to the X-ray tube 11. The fluoro brightness control 25 may be manually adjusted to set the kv. to a desired level by a control device not shown.

The automatic adjustment of the kv. may be accomplished through utilization of a phototimer 28, which is a light integrator, widely utilized in the direct film radiography technology, which integrates time and intensity for each cine frame and may be adjusted to produce a signal when optimum film density is obtained. The phototimer 28 receives signals from a standard photodiode 29, via line 28a, indicative of various intensity levels. When the phototimer 28 receives an intensity signal from the photodiode 29, and integrates that signal and determines that the predetermined optimum film density level has been established, the phototimer 28 will send a signal to a density computer 30 via line 28b.

The density computer 30 is logic circuit which receives two other signals, maximum and minimum exposure signals from a variable maximum limit timer 31 and a variable minimum limit timer 32 via lines 31a and 32a, respectively. A line 31b connects the variable maximum limit timer 31 to the variable minimum limit timer 32 to maintain a relationship between the timers, e.g., the minimum exposure time limit will be some set percentage less than the maximum exposure time limit. The variable maximum limit timer 31 and the variable limit minimum timer 32 may be adjusted to provide pulses to the density computer indicative of the maximum and minimum exposure time limits, respectively.

If the phototimer 28 produces a signal within the minimum and maximum exposure time limits, then the density computer 30 will send a signal to the bias switch circuit 13 via line 31a, which cuts off the X-ray tube 11. However, if the phototimer 28 produces a signal before the variable minimum limit timer 32 sends a signal to the density computer 30, the density computer will produce two output signals upon receiving the phototimer signal, a first output signal to the bias switch circuit 13 to cut off the X-ray tube 11 and a second output signal to the automatic kv. servomotor 26, via line 30a, to adjust the kv. to a lower level. On the other hand, if the phototimer 32 does not produce a signal before the density computer 30 receives a signal from the variable maximum limit timer 31, the density computer 30 will again produce two output signals, a first output signal to the bias switch circuit 13 to cut off the X-ray tube 11 and a second output signal to the automatic servomotor 26, via line 30a, to adjust the kv. to a higher level. Thus, one output of the density computer 30, via line 30a, may then be utilized to automatically adjust the kv. eventually applied to X-ray tube 11 by means of the automatic kv. servomotor 26 and the automatic kv. regulator 27, while the other output controls the bias switch circuit 13.

In the operation of the cine fluororadiographic apparatus 10, a typical situation would involve a fluoroscopy which precedes any cine film. During the fluoroscopy, the kv. is automatically adjusted by the fluoro brightness control 25. The kv. is automatically regulated via the fluoro kv. sensor 24 cooperating with a standard reference amplifier, not shown, within the fluoro brightness control 25, which in turn controls the automatic kv. servomotor 26 and the automatic kv. regulator 27. The response time of the motor-driven regulator is such that it covers a 60 kv. range in three seconds. This form of automatic density control during fluoroscopy is not new.

The skilled technician has already predetermined the factors to be used during cine filming. For a typical example, he has preset the cine camera 22 to operate at 60 flrams per second, has set the variable maximum limit timer 31 to 5 milliseconds, and has selected a value of 200 milliamperes for tube operation. The variable minimum limit timer 32 has been designed and adjusted to send a pulse to the density computer 30 at a time of 60 percent of that of the variable maximum limit timer 31, which in the present case wold be 3 milliseconds.

When the operator desires cine filming, he actuates an exposure switch, not shown, which accomplishes the following: (1) boosts the X-ray tube filament to a 200 milliampere emission value; (2) automatically directs the image splitting mirror of the lens arrangement 19 so that the output phosphor image is directed into the cine camera 22; (3) connects certain taps on the X-ray control automatic transformer to compensate for the 200 milliampere tube load; (4) energizes the cine camera motor within the cine camera 22; (5) energizes all the circuit components of the variable maximum limit timer 31, the variable rninimum limit timer 32, the phototimer 28, and the kv. regulating circuitry (26 and 27); (6) applies the bias voltage to the cathode of the X-ray tube 11; and (7) closes the power to the primary of the high voltage transformer, not shown in detail.

When the camera shutter opens, a light chopper switch 33 triggers a positive going pulse in the bias switch circuit 13, via line 33a. This positive going pulse cancels the negative bias and allows X-ray tube 11 to conduct. During the initial frame in a typical examination, the X-ray intensity will be too high due to the kv. being too high. The phototimer 28, in attempting to cut the exposure time as short as possible, will produce a necessary exposure time shorter than the limit determined by the variable minimum limit timer 32, that is, shorter than 3 milliseconds. The density computer 30 will recognize this situation and will energize the automatic kv. servomotor 26 to drive the kv. down. After three or four frames, the kv. is lowered to where the X-ray energy is such that the phototimer 28 terminates the exposure after 3 milliseconds. The density computer 30 now recognizes that this is a satisfiactory exposure and the automatic kv. servomotor 26 is turned oif. As long as the phototimer 28 is timing between 3 and 5 milliseconds, the density computer 30 is dormant as the exposure density will be within the correct limit. On the other hand, if there is a change in the density of a body part which requires the phototimer 28 to attempt to time longer than 5 milliseconds, the density computer 30 will recognize this situ ation and it will energize the automatic kv. servomotor 26 to raise the kv. Therefore, as long as the phototimer 30 is timing between 3 milliseconds (minimum time) and 5 milliseconds (maximum time) it is unnecessary to trigger the automatic kv. servomotor 26.

Thus, although the present invention has been shown and described with reference to particular embodiments, for example, a cine fiuororadiographic apparatus automatically operating within defined time limits with particular film, nevertheless, various changes and [modifications obvious to a person skilled in the art to which this invention pertains, for example, time limits of 1 to 3 milliseconds and 90 mm. film, are deemed to lie within the spirit, scope, and contemplation of the invention as set forth in the appended claims.

What is claimed is:

1. A cine fiuororadiographic apparatus comprising:

an X-ray means for generating an X-ray beam;

voltage regulating means connected to said X-ray means for regulating the kv. applied to said X-ray means;

intensifier means receptive to said X-ray beam for producing X-ray images;

light integrator means for determining the film density established by said X-ray images during each respective cine frame;

timers means for providing minimum and maximum time limits; logic means connected to said] light integrator means and said timer means for providing first output signals to cut off the operating bias to said X-ray means and second and third output signals to control said voltage regulator means; and cine means for recording said X-ray images. 2. A cine fiuororadiographic apparatus as recited in claim 1 wherein said X-ray means comprises a grid-controlled X-ray tube, a bias switch circuit for controlling the ma. provided said X-ray tube, a constant potential generator, and collimator means.

3. A cine fiuororadiographic apparatus as recited in claim 2 wherein said voltage regulating means comprises an automatic kv. regulator and an automatic kv. servomotor.

4. A cine fiuororadiographic apparatus as recited in claim 3 wherein light integrator means comprises light detecting means for receiving the intensity of said X-ray images during each respective cine frame and a light integrator having a predetermined optimum film density recognizing level.

5. A cine fiuororadiographic appartus as recited in claim 4- wherein said light integrator means provides an output signal indicative of said optimum film density recognizing level having been established.

6. A cine fiuororadiographic apparatus as recited in claim 5 wherein said timer means comprises a first timer which provides a minimum time limit signal and a second timer which provides a maximum time limit signal.

7. A cine fiuororadiographic apparatus as recited in claim 6:

wherein logic means is adapted for receiving said light integrator means output signal, and is further adapted for receiving said minimum time limit signal and said maximum time limit signal from said first timer and said second timer, respectively; wherein said logic means is adapted for providing a first output signal to cut oil said operating bias to said X-ray means if said light integrator output signal arrives at said logic means between the period that said first timer output signal and said second timer output signal arrive at said logic means;

wherein said logic means is adapted for providing said first output signal to cut oil said operating bias to said X-ray means and said second output signal to said voltage regulating means for lowering the kv. applied to said X-ray means if said light integrator output signal arrives at said logic means prior to the time that said first timer output signal is due to arrive at said logic means; and

wherein said logic means is adapted for providing said first output signal to cut oil said operating bias to said X-ray means and a third output signal to said voltage regulating means for raising the kv. applied to said X-ray means if said second timer output signal arrives at said logic means prior to the time that said light integrator output signal arrives at said logic means.

8. A cine fiuororadiographic apparatus as recited in claim 7 wherein said cine means comprises a cine camera and a control circuit including a light chopper switch means for providing a trigger to allow said grid-controlled X-ray tube to conduct.

9. A cine fiuororadiographic apparatus as recited in claim 8 wherein said cine camera is a 16 mm. variable frame rate camera.

10. A cine fiuororadiographic apparatus as recited in claim -8 wherein said cine camera is a 35 mm. variable frame rate camera.

11. A cine fiuororadiographic apparatus as recited in claim 8 wherein cine camera is a mm. variable frame rate camera.

12. A cine fluororadiographie apparatus as recited in claim 1 wherein said timer means is adjustable for providing said minimum time limit at a fixed percentage of said maximum time limit.

13-. A cine fluororadiographic apparatus as recited in claim 6 wherein said minimum time limit signal and said maximum time limit signal are provided 3 and 5 milliseconds, respectively, after the exposure of a cine frame.

14. A cine fluororadiographie apparatus as recited in claim 1 wherein said logic means includes a density computer having a first input from said light integrator and a second and third input from said timer means, said density computer further having a first output to said voltage regulating means and a second output to said voltage regulating means.

References Cited ARCH-IE R. BORCHELT, Primary 'Examiner US. Cl. X.R. 25065, 77 

